As the above-mentioned accumulator, there is known one of a type which arranges a gas-liquid separating plate at the inside and makes the gas/liquid dual phase refrigerant strike it, as shown in for example FIG. 9 of PLT 1. FIG. 5 is a view which shows an accumulator of FIG. 9 of PLT 1. This accumulator is provided with an inlet 105 and outlet 106 of a fluid which are arranged in parallel at a top part of a pressure vessel 102, a double wall tube 108 which guides the gas refrigerant to the outlet, and a gas/liquid separating plate (umbrella-shaped member) 115 which spreads out in a substantially conical shape or umbrella shape so as to cover a gas refrigerant inflow port of the double wall tube 108. The gas/liquid dual phase state refrigerant which flows in from the inlet 105 is separated into a gas and liquid by striking the umbrella shaped member 115 whereby the gaseous refrigerant flows through a circumferential gap S3 between the umbrella shaped member 115 and the inside surface of the pressure vessel 102, flows from the top end of the outside tube 110 of the double wall tube to the inside of the double wall tube, descends, then rises inside the inside tube 109 and is sent from the outlet 106 to a compressor (not Shown). The separated liquid refrigerant and oil which had been contained in the refrigerant flow down through the circumferential gap S3 between the umbrella shaped member and the inside wall of the vessel to be stored at the bottom part of the vessel.
In this regard, in the accumulator of FIG. 9, the flow cross-sectional area changes so as to expand while transitioning from the inflow port 105 to the space S2 above the umbrella shaped member 115, then being reduced at the circumferential gap S3 between the umbrella shaped member 115 and the vessel inside surface, but a relatively large pressure loss of the refrigerant occurred due to this change of the flow cross-sectional area.